Linear Technology Corp.’s LTC6400-20 and LTC6401-20 are ADC drivers that achieve unprecedented performance on a single 3 V supply. These fully differential amplifiers include gain setting resistors, simplifying the challenge of driving the highest performance high-speed ADCs. The LTC6400-20 provides a fixed gain of 20 dB with –93 dBc third-order intermodulation distortion (IMD₃) performance and noise figure of 6.5 dB for a 140 MHz input frequency. At 240 MHz, IMD₃ is better than -70 dBc. Other family members with fixed gains ranging from 8 dB to 26 dB will follow, said the manufacturer.

The driver provides a differential output voltage swing of 4.4 V_P-P. In addition to minimizing power consumption, this eliminates the need for a separate 5 V supply in applications using the latest 3 V and 3.3 V ADCs. To further simplify interfacing to high-speed ADCs such as the LTC2208, a V_OCM pin sets the output common mode voltage of the LTC6400-20 to match the input range of the ADC. An optional on-chip filter helps to handle charge injection common to the capacitive inputs characteristic of pipelined ADCs. Inputs may be AC- or DC-coupled. While fully differential, the LTC6400-20 can be used to easily convert single-ended inputs to differential outputs.

The LTC6401-20 is a lower-power part optimized for lower input frequencies. Consuming just 50 mA, half that of the LTC6400-20, the LTC6401-20 maintains the same low noise performance and –90 dBc distortion performance for input frequencies up to 70 MHz.

These parts are available in a tiny 3 mm x 3 mm 16-lead QFN package. In 1,000-piece quantities, LTC6400-20 is priced at $3.68 each and the LTC6401-20 at $2.95.

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